The rapid and accurate detection of visible and invisible substances, including target molecules and microorganisms is critical for many areas of research, environmental assessment, food safety, medical diagnosis, air quality assessment, homeland security, illicit drug identification, and warfare. In fact, diagnostic assays of biological compounds have become routine for a variety of applications, including medical diagnosis, forensic toxicology, pre-employment, insurance screening, and foodborne pathogen testing.
Industrial demand for low-cost, sensitive, rapid assays with the potential for screening multiple analytes simultaneously or in rapid succession has caused the development of many testing systems and formats. Most systems can be characterized as having three key components: a probe that recognizes the target analyte(s) with a high degree of specificity; a reporter that provides a signal that is qualitatively or quantitatively related to the presence of the target analyte; and a detection system capable of relaying information from the reporter to a mode of interpretation.
To ensure accuracy, the probe (e.g., antibody or nucleic acid sequence) should interact uniquely and with high affinity to the target analyte, but be non-reactive to non-targets. In order to minimize false positive responses, the probe should be non-reactive with and have no cross-reaction to non-target analytes.
Often, a label is directly or indirectly coupled (conjugated) to the probe. The label provides a signal that is related to the concentration of analyte upon completion of the assay. Ideally, the a label is not subject to signal interference from the surrounding matrix, either in the form of signal loss from analyte extinction or by competition from non-specific signals (noise) from other materials in the system.
A detector is usually a device or instrument used to determine the presence of the reporter (and therefore the analyte) in a sample. Some devices utilize a detector that provides an accurate and precise quantitative scale for the measurement of the analyte. Other devices, such as rapid on-site tests, such as pregnancy tests, utilize a detection instrument that provides the test results as a qualitative (positive or negative) signal. This signal may be visual.
Immunochromatographic assays have been known in the art for some time. These include, but are not limited to, lateral flow tests (e.g., lateral flow strips), for detecting analytes of interest. A typical lateral flow test utilizes the concept of lateral liquid or suspension flow in order to transport a given sample to the test. The benefits of lateral flow tests include a user-friendly format, rapid results, long-term stability over a wide range of climates, and relatively low cost to manufacture. These features make lateral flow tests well-suited for applications involving drug testing in urine and saliva in the workplace or retail markets, rapid point-of-care testing in hospitals and doctor's offices, as well as testing in the field for various environmental and agricultural analytes.
Most lateral flow tests are directed to fluid samples and may require several separate materials or parts in a kit in order to perform and/or optimize detection of a target analyte. Current lateral flow tests require some means for collecting the sample and then a means of exposing the sample to probes specific to the target analyte. Urine samples for drug testing are normally collected into a container and then the lateral flow strip is dipped into the sample. The sample travels up the lateral flow strip and if a drug is present binds to available antibodies which causes a reaction that can be visually detected on the strip. Applying this technology to surface, air and fluid testing has been problematic resulting in cumbersome testing procedures that have limitations. For example, applying the sample to be tested directly to the lateral flow strip disturbs the flow of the materials on the strip and hence the results of the test. Applying the sample directly to the lateral strip also limits the areas available to be tested to clean dry areas where there no grease or other debris is present to interfere with the flow on the strip. Also, the material supplied to initiate the reaction, distilled water droplets from a separate water dropper, freezes and as such the test can not be performed in below freezing climates. Moreover, having a separate device for dropping water to initiate the lateral flow reaction is cumbersome, costly and difficult to use.
Additional materials that can be provided with the lateral flow test include a separate vial containing a buffer solution or water to start the lateral flow reaction, a wick to transport the sample to the test; a filtration material to remove unwanted particles; a conjugate release pad where the detection reagent(s) is immobile when dry but mobilized when wet; and a reaction matrix where the capture reagents are immobilized. Unfortunately, in all of these cases, at least two separate devices (i.e., one device for collecting the sample and another device for detecting target analytes) and multiple steps are required to perform the test. Our invention simplifies and improves upon the previous inventions in this field.
Further, lateral flow tests are frequently subject to flow problems due to the nature of the chemistry and flow of reagents and sample. Any alteration of the test strip can alter the dynamics of the chemistry and reaction of the strip in the present of a target analyte. These tests usually require complex, multipart assays performed on a series of overlapping pads of different types of materials aligned on a test strip. Problems arise from, for example, material incompatibility, contact issues, and imperfect material characteristics. Boundaries found between segments can adversely affect flow characteristics. Different materials may have widely different flow, or wicking, rates, which have different effects on molecules flowing through them. Other problems that exist include contamination of the sample by interfering materials in the matrix, by contact with collector/operator; insufficient sample size due to inadequate “washing”; and operator/collector error when utilizing devices that require multiple devices/parts and steps necessary to test a surface for a target analyte.
Thus, it would be desirable to have a single self-contained device for collecting, extracting, testing, and a system of shipping the original untested material under forensic chain of custody a sample collected from a surface, powder, pill or fluid or sample of air that is easy to operate and not limited by dirty, greasy or wet contaminates and is stable under a wide variety temperatures and field conditions. The subject invention solves the above limitations in a self-contained device by first collecting samples on a built-in, specially treated swab and then washing the target analytes off the swab into a temperature stable buffer solution prior to testing. This approach does not limit the type of sample tested as the target analyte does not overload or disrupt standard lateral flow technology and is applicable to a wide variety of analytes and detection technologies. While the subject invention has been optimized for the drugs of abuse market, it is not limited or intended to just testing for drugs of abuse and can be used to test for a wide variety of substances such as explosives, WMD's, food toxins and industrial waste in dusts, powders, air, biological and non biological liquids with the same basic device.